The present invention relates to magnetic resonance imaging (MRI) systems, and more particularly, to a receiving coil having geometrically isolated multiple quadrature coils.
Receiving coils are used in magnetic resonance imaging systems to intercept the radio frequency magnetic field generated by a human subject or object in the presence of a main magnetic field. The radio frequency signals are in the form of a circularly polarized or rotating magnetic field, having an axis of rotation aligned with the main magnetic field.
Chronologically, the receiving coil first took the form of a volume coil which is designed to enclose a volume for receiving a body part, such as a leg, arm or head. See, for example, U.S. Pat. Nos. 4,411,270 to Damadian and 4,923,459 to Nambu. The surface receiving coil was then developed which is designed to be placed adjacent the region of interest. For a surface receiving coil, see, for example, U.S. Pat. No. 4,793,356 to Misic et al.
Advances in the field have resulted in modifications to volume and surface receiving coils to improve their signal-to-noise ratio. This was achieved by modifying the coils to pick up perpendicular components of the radio frequency magnetic resonance field. These coils are known as quadrature coils, which coils have a significant signal-to-noise ratio improvement over their non-quadrature counterparts. See, for example, U.S. Pat. Nos. 4,467,282 to Siebold and 4,707,664 to Fehn.